Optical Fiber Preform UV Defect Reduction
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Solution Overview
Problem
Existing methods for producing optical fiber preforms result in fibers with low initial transmission and high susceptibility to short-wave UV radiation due to the formation of defects and precursor centers during the deposition process, particularly caused by the UV portion of the plasma flame.
Innovation Solution
A plasma flame emitting ultraviolet light at 214 nm with an intensity of at least 0.9 μW is used to deposit SiO2 particles on the core glass cylinder, reducing defect formation and enhancing the intrinsic absorption of the core glass cylinder, thereby reducing the impact of UV radiation and improving the resistance to short-wave UV radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a plasma burner is used to deposit SiO2 particles on the core glass cylinder, then the cladding glass layer can be formed efficiently, but UV radiation from the plasma flame creates defects and precursor centers that reduce transmission and increase susceptibility to UV damage
Solution Approach 1:
The patent converts the harmful UV radiation from the plasma flame into a beneficial effect by carefully controlling the deposition process to create a specific defect structure in the cladding layer that acts as a protective barrier. The UV radiation, which would normally damage the core glass, is instead used to create precursor centers in the cladding that prevent deeper penetration of harmful radiation and reduce overall defect formation in the fiber.
Solution Approach 2:
The patent applies parameter changes by precisely controlling plasma flame parameters (power, gas composition, flow rates) and deposition parameters (rotation speed, deposition rate, temperature) to optimize the balance between forming a dense cladding structure and minimizing harmful UV-induced defects. By adjusting these parameters, the process achieves both efficient deposition and reduced susceptibility to UV damage.
2Productivity
If the plasma flame intensity is increased to improve deposition rate, then productivity increases, but defect formation and precursor centers increase leading to lower transmission
Solution Approach 1:
The patent employs parameter changes by optimizing the plasma flame power, gas composition ratios, and deposition conditions to achieve a specific window where sufficient deposition rate is maintained while defect formation is minimized. This involves precise control of RF power, oxygen and silicon precursor flow rates, and substrate temperature to balance productivity with manufacturing precision.
3Reliability
If fluorine doping is applied to the cladding glass to improve refractive index profile, then optical performance improves, but the complexity of the deposition process increases
Solution Approach 1:
The patent merges the fluorine doping process with the SiO2 deposition process by introducing fluorine-containing precursors simultaneously with silicon precursors in the plasma flame. This combined approach allows formation of the fluorine-doped cladding layer in a single deposition step rather than requiring separate doping and deposition processes, thereby improving optical performance while managing process complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method produces optical fibers with higher initial transmission and improved resistance to UV radiation, characterized by reduced attenuation and fewer defects, especially in the UV wavelength range, making them suitable for high-energy UV applications like excimer laser radiation.
Implementation Method 1
a silicon-containing starter substance is supplied to a plasma burner, said substance being oxidized in a plasma flame assigned to the plasma burner to obtain SiO2 particles
Implementation Method 2
a plasma flame which emits ultraviolet light of a wavelength of 214 nm with an intensity of at least 0.9 μW
Implementation Method 3
enhancing the intrinsic absorption of the core glass cylinder, thereby reducing the impact of UV radiation
Implementation Method 4
the SiO2 particles are deposited in layers on the cylindrical outer surface of the core glass cylinder
Implementation Method 5
and said particles being sintered
Implementation Method 6
are directly sintered onto the core glass layer with formation of a fluorine-containing SiO2 cladding glass layer
Data Source
AI summary
In a known method for the production of a blank mold for optical fibers, a fluorine-doped SiO2 enveloping glass is produced on a core glass cylinder that rotates about its longitudinal axis, wherein a silicon-containing starting substance is fed to a plasma burner, said substance is then oxidized in a plasma flame assigned to the plasma burner to obtain SiO2 particles, the SiO2 particles are deposited by layers on the enveloping surface of the cylinder of the core glass cylinder in the presence of fluorine and sintered into the enveloping glass. The invention aims at providing an economical method, which builds upon the above-mentioned method, in order to produce a blank mold from which optical multi-mode fibers (52) can be obtained. In comparison with fibers (51) produced according to standard methods, said optical multi-mode fibers are characterized by high initial transmission in the UV wavelength range and good resistance with respect to brief UV radiation, more particularly in the 210-300 nm wavelength range. According to the invention, a plasma flame that irradiates an ultraviolet light having a wavelength of 214 nm with an intensity of at least 0.9 ?W—determined on the basis of plasma flame intensity measurement—is used for the formation and deposition of the SiO2 particles on the core glass.